Re: Keeping separate WAL segments for each database

Robert Haas <robertmhaas@gmail.com> writes:
> You need to make sure not only that you replay commit records in
> order, but also that, for example, you don't replay an
> XLOG_HEAP2_CLEAN record too early.

Hm, good point.  That probably means that you *do* need fencepost
records, and furthermore that you might need an interlock to ensure that
you get the fencepost in early enough on the other stream.  Ugh ---
there goes your concurrency.

What about having a single WAL stream for all commit records (thereby
avoiding any possible xact-serialization funnies) and other WAL records
divided up among multiple streams in some fashion or other?  A commit
record would bear minimum-LSN pointers for all the streams that its
transaction had written to.  Things like HEAP_CLEAN records would bear
minimum-LSN pointers for the commit stream.  Workable?
        regards, tom lane